Friction closure



May 24, 1966 FIG. I

R. F. BATEMAN FRICTION CLOSURE Filed Aug. 15, 1964 INVENTOR ROBERT F.BATEMAN ATTORNEYS United States Patent 3,252,446 FRICTION CLOSURE RobertF. Bateman, Woonsocket, R.I., assignor to The Carters Ink Company,Cambridge, Mass, a corporation of Massachusetts 4 Filed Aug. 13, 1964,Ser. No. 389,328 2 Claims. (Cl. 120-4101) This invention relatesgenerally to closure constructions and more particularly to theconstruction of closures employing frictional engagement as theoperating principle thereof.

With the growing widespread use of new materials, such as plastics, andthe current trend toward greater sophistication in packaging, variousnew closure designs have been produced to satisfy the aesthetic andpractical requirements of contemporary commerce. Whereas at an earliertime almost all containers to which removable caps were fitted employeda screw-threaded closure construction with cooperating threads locatedon the container neck and the cap, numerous different constructions arecurrently employed. Where the container is to hold a fluid, a dispensingclosure is often permanently fitted to the container body and includes aclosa'ble aperture through which the contents may be dispensed asdesired.

In other instances, typically with respect to writing in: struments, itis necessary to provide a totally removable cap which, when removed,exposes the writing point for use and which, when in place, bothprotects the Writing point and retains any possible writing fluid whichmay leak from the body of the container past or through the writingpoint.

For many years, almost all pens and similar drawing instruments wereprovided with screw-threaded caps. As new, more economical constructionmaterials were employed for the writing instrument bodies and caps, itwas also desired to eliminate the screw-thread closures. To this end,many writing instruments have for some time been provided with a type offriction closure which typically employs a cap having a slightly greaterdiameter than the body of the writing instrument over which it isfitted. The body, or the cap, is usually provided with some compressiblemeans which frictionally engages the other member and retains the capupon the body of the writing instrument. Flat springs mounted within thecap and resilient O-rings mounted about the body are commonplacecontemporary constructions.

An even more efficient and less expensive frictional closure which isparticularly adapted for use with writing instruments and the like,employs a pair of generally mating nesting surfaces, one of which ispositioned about the exterior of the container body and the other ofwhich forms an interior wall on the cap. The cap is engaged by nestingthe pair of surfaces which have substantially identical diameters.Containers employing this closure construction are substantially lessexpensive to manufacture since no additional parts, springs, O-rings andthe like are required. The construction is also relatively easy to usesince the container is securely closed, at least in theory, simply byinserting the cap over the neck ofthe container and pushing it thereonas far as it will go. Despite the attractiveness of this construction,it has not met with substantial acceptance because of a severelimitation with respect to the amount of frictional engagement possiblebetween the container and its cap. The conventional container having anelongated neck over which the friction cap is to be inserted may besecurely closed by frictional engagement of the cap with the neck atonly a limited portion of the neck area. area of frictional engagementbetween the nesting surfaces is located adjacent the base of the necksurface;

The

Conventionally, the Walls of the neck surface converge from the commondiameter more rapidly than those of the cap thereby defining the lowerportions of both the cap and the neck as the area of frictionalengagement. The height of this area along the principal axis of the neckand cap need only be sufficient to insure that the frictional engagementwill not be destroyed and the cap dislodged by accident. At the sametime, however, it is necessary that the area of frictional engagement besmall enough that the cap may 'be removed relatively easily by pullingit off of the neck of the container. Substantial difiiculty has beenencountered in designing a frictional engagement closure whichsatisfactorily satisfies both the requirement of secure seating of thecap and that of easy removal. The cap has either been nested so stronglythat the frictional engagement is extremely difficult to overcome, oralternatively, the area of frictional engagement has been so small thatthe cap may he accidentally dislodged or may fail to engage at all aftera period of use.

It is, accordingly, a major object of this invention to construct afriction closure which includes sufficient frictional area to securelymaintain the parts in engaged relation while permitting easydisengagement thereof when desired.

It is a further object of this invention to construct a friction closurewhich may be easily and inexpensively manufactured and will be suitablefor use with relatively small containers as for example writinginstruments and the like.

In the construction of a preferred embodiment of the invention thewriting instrument employs a closure having a removable cap which isheld "by frictional engagement between its inner surface and the outersurface of a neck on the body of the instrument. The area of frictionalengagement between these nesting surfaces is of sufficient size thatsubstantial difficulty is encountered in overcoming the coefficient offriction between the surfaces to dislodge the cap from the writinginstrument. In order to provide easy disengagement of the cap whendesired, a plurality of cooperating camming surfaces are formed on thecap and the instrument body to cooperate with each other along the lineof closure. When it is desired to remove the cap from the closure it isonly necessary to rotate the cap about its principal axis in eitherdirection, thereby more easily overcoming the frictional engagementbetween the parts, which rotation is translated through the cooperatingcamming surfaces positioned about the line of closure into displacementof the cap longitudinally from the writing instrument.

It is a feature of the invention that the friction bond between thenested cap and container is initially overcome by relative rotarymovement therebetween following which the cap is displacedlongitudinally from the container neck.

It is a further feature of the invention that a substantial area offrictional engagement may be employed between the cap and the containerto insure that the cap may not be accidentally dislodged and further toinsure that normal distortion of the cap through use will not destroythe area of frictional engagement.

These and other objects and features of the invention will be morereadily understood and appreciated from the following detaileddescription of a preferred embodiment thereof selected for purposes ofillustration and shown in the accompanying drawings, in which:

FIG. 1 is a view in side elevation of a container cap "constructedaccording to the invention;

FIG. 2 is a view in side elevation of a container constructed to receivethe cap of FIG. 1;

FIG. 3 is a section taken on the line 33 of FIG. 1;

FIG. 4 is a section taken on the line 4-4 of FIG. 2;

FIG. 5 is a view in side elevation of thecap of FIG. 1 and the containerbody of FIG. 2 in nested, engaged relation; and

FIG. 6 is a view in side elevation showing the cap and body of FIG. 5during disengagement thereof.

In FIGS. 1 and 2 a container body 10 is shown. At the top of the body 10is a frusto-conical shank or neck 12 from which extends a marking felt14; and forming, in the preferred embodiment, the body of a generallycylindrical felt tip marker. The body 10 is normally filled with markingfluid which is dispensed by the felt 14.

A cap 16 is provided for engagement on the body 10. The cap 16 includesan internal frusto-conical bore 18 into which the neck 12 of the body 10may be nested. The exterior configuration of the body 10 and the cap 16is a matter of design only and forms no portion of this invention.

In FIG. 5 an angular line of closure 20 is shown between the body 10 andthe cap 16 when they are fully nested. When the cap 16 is fully engagedon the body 10, the exterior surface of the neck 12 is in frictionalengagement with a portion of the bore 18. The area of frictional contactis indicated generally at 22 in FIGS. 1 and 2 respectively. The extentto which the frictional contact area 22 extends upwardly along the neck12 and upwardly from the open end of the bore 18 will depend in eachinstance upon the particular application. The proportions shown in FIGS.1 and 2 are, however, typical. The extent of the frictional contact area22 is determined by the selection of angles for the nesting surfaces onthe neck 12 and the bore 18. Generally speaking, the neck 12 has anangle included between its base and side wall which is smaller than theangle between the base and side wall of the bore 18. The two angles areinitially selected of sufiicient size, however, that the nestingsurfaces are in frictional contact through an area of sufficient size toprovide a secure fit.

In order to disengage the cap 16 from the body 10 a plurality of cammingsurfaces 24 are provided on the body 10 about the base of the neck 12.The camming surfaces 24 are contiguous spiral segments alternatelysloping in opposite axial directions and form a plurality of generallyangular upstanding shoulders 26 about the base of the neck 12. Theheight of the camming surfaces 24 and hence of the shoulders 26 issubstantially the same as the height of the area of frictionalengagement of the neck 12.

Depending camming surfaces 28 are formed about the base of the cap 16 atthe entrance to the bore 18 to cooperate with the camming surfaces 24 onthe body 10. The camming surfaces 28 on the cap 16 likewise form aplurality of generally angular depending shoulders 30 positioned aboutthe base of the cap 16. The camming surfaces 28 on the cap 16 mate withthe camming surfaces 24 on the body 10 when the cap 16 is inserted overthe neck 12 and abut along the angular line of closure 20.

FIG. 6 shows the cooperation of the camming surfaces 24 and 28 to causethe depending shoulders 30 on the cap 16 to ride upwardly upon theupstanding shoulders 26 on the body 10 during relative rotation of thecap 16 with respect to the body 10. It will be noted that since theheight of the shoulders 26 and the shoulders 30 is substantially thesame as the height of the area of the frictional engagement 22 it ispossible to free the cap 16 for easy removal by displacing it axiallyalong the neck 12 a distance equal to the height of either the shoulder26 or the shoulder 30. Because of the extensive area of frictionalengagement 22, as desired to maintain the cap securely in place, itwould, however, be extremely difficult to withdraw the cap from thecontainer by simply exerting an axial separating force.

As is well known, the effort required to overcome frictional engagementin the area 22 is substantially greater when a force is applied toseparate the surfaces axially than when a force is applied to causerelative rotation between the two parts. Rotation alone will not,however, dislodge the cap 16 from the neck 12 and translation of therotary motion to axial motion has heretofore required a cessation ofrotary motion thereby re-establishing the frictional bond between thecap 16 and the neck 12.

It will also be noted that a mechanical advantage is achieved indisengaging the cap from the neck since the outside diameter of the cap,which is grasped by the user, is substantially greater than the interiordiameter thereof which defines the area of frictional engagement.

By providing the novel camming surfaces 24 and 28 it is possible totranslate relative rotary motion between the cap 16 and the neck 12gradually and without cessation into axial motion tending to displacethe two parts. Hence, once the frictional bond is destroyed by relativerotation the cap 16 may be removed without re-establishing the bondthrough the operation of the co-operating camming surfacescausing theshoulders 26 and 30 to ride against each other thereby displacing thecap 16 axially along the neck 12 beyond the area of frictionalengagement 22.

It will thus be noted that through the operation of the camming surfacesand the shoulders of the invention it is possible to first overcome thefrictional engagement of two members having partially mating nestingsurfaces by the application of a relative rotary motion which istranslated through the operation of the camming surfaces and theshoulders into an axially displacing motion. With the construction ofthis invention it is now possible to provide a substantially greaterarea of frictional engagement between the nesting surfaces providing asubstantially better friction seal thereby permitting the use of thisless expensive, more easily fabricated construction for a plurality ofcontainers the caps of which it is important should not he accidentallydislodged.

While in the illustrated preferred embodiment three cooperatingshoulders and their adjacent camming surfaces are shown continuouslyabout the line of closure of the container, it will be understood thatmore or less cooperating shoulders may be employed. However, although asingle shoulder and the adjacent pair of camming surfaces on eachmember-will suffice, seating of the cap 16 upon the body 10 is howeverfacilitated by a continuous array of shoulders and camming surfaces.Since each shoulder is formed of a pair of camming surfaces it will beunderstood that there will always be an even number of camming surfaces.

Having thus disclosed and illustrated a preferred embodiment of theinvention it is my intention to claim all changes and modificationsthereof.

What I claim as new and desire -to secure by Letters Patent of theUnited States is: v

1. In a closable container comprising a body having an openingterminating in a neck and a closure cap having a bore nestable with saidneck with at least a portion of said neck being in frictional engagementwith a corresponding portion of said bore;

means facilitating the removal of said cap comprising (a) an even numberof equal contiguous spiral segments alternately sloping in oppositeaxial directions to form a series of angular upstanding shoulders onsaid body and completely surrounding said neck, and

(b) corresponding equal contiguous spiral segments alternately slopingin opposite axial directions to form a corresponding series of angularupstanding shoulders on said closure cap in face to face slidingengagement with the segments on said body whereby twisting said closurecap in either direction results in a camming action between saidsegments effective to move said cap away from said body.

2. In a closure for a writing instrument which includes a body and agenerally frusto-conical neck terminating in a writing tip and a caphaving a bore receiving said neck in frictional engagement therewith:

means facilitating the removal of said cap comprising a) an even numberof equal contiguous spiral segments alternately sloping in oppositeaxial directions to form a series of angular upstanding shoulders onsaid body and completely surrounding said neck, and (b) correspondingequal contiguous spiral segments alternately sloping in opposite axialdirections to form a corresponding series of angular upstandingshoulders on said Cap in face to face sliding engagement with thesegments on said body,

References Cited by the Examiner UNITED STATES PATENTS Wing 12042McKelvy 21546 Hoffmann 2i15-46 Ruetz 215-46 JOSEPH R. LECLAIR, PrimaryExaminer.

R. PESHOCK, Assistant Examiner.

2. IN A CLOSURE FOR A WRITING INSTRUMENT WHICH INCLUDES A BODY AND A GENERALLY FRUSTO-CONICAL NECK TERMINATING IN A WRITING TIP AND A CAP HAVING A BORE RECEIVING SAID NECK IN FRICTIONAL ENGAGEMENT THEREWITH; MEANS FACILITATING THE REMOVAL OF SAID CAP COMPRISING (A) AN EVEN NUMBER OF EQUAL CONTIGUOUS SPIRAL SEGMENTS ALTERNATELY SLOPPING IN OPPOSITE AXIAL DIRECTIONS TO FORM A SERIES OF ANGULAR UPSTANDING SHOULDERS ON SAID BODY AND COMPLETELY SURROUNDING SAID NECK, AND (B) CORRESPONDING EQUAL CONTIGUOUS SPIRAL SEGMENTS ALTENATELY SLOPPING IN OPPOSITE AXIAL DIRECTIONS TO FORM A CORRESPONDING SERIES OF ANGULAR UPSTANDING SHOULDERS ON SAID CAP IN FACE TO FACE SLIDING ENGAGEMENT WITH THE SEGMENTS ON SAID BODY, WHEREBY TWISTING SAID CAP IN EITHER DIRECTION RESULTS IN A CAMMING ACTION BETWEEN SAID SEGMENTS EFFECTIVE TO MOVE SAID CAP AWAY FROM SAID BODY. 